Mucinous Cystic Neoplasm of the Pancreas: Understanding Your Pathology Report

by Stephanie Reid MD FRCPC
June 16, 2026

A mucinous cystic neoplasm (MCN) is a cyst-forming tumor of the pancreas made up of cells that produce a thick, sticky substance called mucin. It occurs almost exclusively in women, most often around 40 to 50 years of age, and is usually found in the tail (the end) of the pancreas, although it is occasionally found in the head. Most mucinous cystic neoplasms are benign (non-cancerous) and can be cured with surgery. However, they are considered to have malignant potential, which means that a small number can develop into pancreatic cancer over time if not removed.

This article will help you understand the findings in your pathology report, what each term means, and why it matters for your care.

What causes a mucinous cystic neoplasm?

The exact cause of a mucinous cystic neoplasm is not known. Because these tumors occur almost entirely in women and contain a special type of tissue that resembles tissue normally found in the ovary, doctors believe that hormones may play a role in their development. There are no strong, well-established risk factors, and most are found by chance rather than because of a known cause.

What are the symptoms of a mucinous cystic neoplasm?

Mucinous cystic neoplasms tend not to cause symptoms until they become large, and they are usually found during imaging done for another reason. When symptoms do occur, they may include discomfort or pain in the upper abdomen, a feeling of fullness, or a palpable mass. Larger tumors may press on nearby organs.

How is the diagnosis made?

The workup usually begins with imaging studies such as CT, MRI, or endoscopic ultrasound (EUS), which may reveal a pancreatic cyst. During an EUS, a thin needle can sometimes be used to remove a sample of fluid and cells from inside the cyst, in a fine-needle aspiration or core-needle biopsy. The fluid can be tested for certain proteins and sugars, and for changes in genes such as KRAS, which help suggest that a cyst is mucinous.

For many patients, a definitive diagnosis can only be made after the entire tumor is surgically removed and examined under the microscope by a pathologist. Under the microscope, the tumor consists of one or more open spaces called cysts. The inside of the cysts is lined by tall, mucin-producing cells. What makes a mucinous cystic neoplasm unique is a distinctive layer of tissue in the cyst wall, just beneath the lining cells, that looks like tissue normally found in the ovary. This “ovarian-type stroma” is required for the diagnosis and separates a mucinous cystic neoplasm from other pancreatic cysts. Unlike an intraductal papillary mucinous neoplasm (IPMN), a mucinous cystic neoplasm does not connect with the pancreatic duct system.

Grade (degree of dysplasia)

Dysplasia describes how abnormal the lining cells look under the microscope. Every mucinous cystic neoplasm has some degree of dysplasia, and the tumor is graded according to the most abnormal area found. Dysplasia is not cancer, but a small number of these tumors with dysplasia can turn into cancer over time if they are not completely removed.

Low grade dysplasia — The lining cells look only mildly abnormal. Most mucinous cystic neoplasms fall into this group and behave benignly once completely removed.
High grade dysplasia — The lining cells look much more abnormal and are closer to becoming cancer. High grade dysplasia is less common and carries a higher risk of an associated invasive cancer.

Knowing the grade of dysplasia helps the treatment team assess risk and decide how the tumor should be managed and monitored.

Can a mucinous cystic neoplasm become cancer?

Yes, although most do not. In a minority of cases, a type of cancer called adenocarcinoma develops from within a mucinous cystic neoplasm. The risk is higher when the tumor shows high grade dysplasia, when it is large (often cited as greater than about 4 to 5 cm), and when imaging or pathology shows a solid nodule growing in the wall of the cyst. When invasive cancer is present, it is staged and managed like pancreatic ductal adenocarcinoma, and the outlook then depends on the type and extent of that cancer.

Surgical margins

A margin is the edge of the tissue that is cut during surgery to remove the tumor. The pathologist examines these edges under the microscope to see whether any tumor cells reach them. The number of margins depends on the type of surgery performed.

Negative margin — No tumor cells are seen at the cut edge. This suggests the tumor was completely removed. The pathologist may also record the distance between the tumor and the closest margin.
Positive margin — Tumor cells are seen right at the cut edge. This means some of the tumor may have been left behind. If dysplasia reaches the margin, the area left behind could continue to develop over time, and the treatment team may consider further surgery or closer follow-up.

In pancreatic surgery, the margins commonly examined include the pancreatic margin (where the pancreas was cut), the common bile duct margin, the uncinate (retroperitoneal) margin behind the pancreas, and, when part of the stomach or small intestine (duodenum) is removed, the edges of those organs.

What is the prognosis?

The outlook for a mucinous cystic neoplasm is generally excellent. Most tumors show only low grade dysplasia and are cured by complete surgical removal, with little or no risk of the tumor returning afterward. Tumors with high grade dysplasia also have a very good outlook when they are completely removed before an invasive cancer has developed. When an invasive cancer is present, the outlook depends on the type and stage of that cancer, although a cancer found within a mucinous cystic neoplasm and removed early tends to do better than conventional pancreatic cancer. Because the tumor is usually cured by surgery, the main role of follow-up is to confirm complete removal.

What happens after the diagnosis?

What happens next depends on the size of the tumor, its location, and the findings on imaging and pathology. Because mucinous cystic neoplasms have malignant potential and most occur in the body or tail of the pancreas, surgery to remove the tumor is often recommended. A tumor in the tail is usually removed with a distal pancreatectomy, while a tumor near the head of the pancreas may require a Whipple procedure, which removes the head of the pancreas along with part of the small intestine and sometimes the stomach. Small tumors without concerning features are sometimes monitored with regular imaging instead of being removed right away, based on current guidelines and a person’s overall health.

When a mucinous cystic neoplasm without invasive cancer is completely removed, no further cancer treatment is usually needed, and care focuses on follow-up imaging. If invasive cancer is found, it is managed like pancreatic ductal adenocarcinoma, which may involve chemotherapy and other treatments. Care often involves a team that may include a gastroenterologist, a surgeon, a radiologist, and a pathologist.

Questions to ask your doctor

Was ovarian-type stroma seen, confirming the diagnosis of a mucinous cystic neoplasm?
Was there low grade or high grade dysplasia?
Is there any evidence of invasive cancer?
How large was the tumor, and was there a solid nodule in the wall?
Was the entire tumor removed, and were the margins negative?
Should my tumor be removed with surgery, or can it be watched with imaging?
Will I need any additional treatment?
What is my risk of the tumor returning or developing cancer in the future?
How often will I need follow-up imaging?